The present invention relates to a tool holder which is used with being attached to a rotary part of a working machine, and more particularly to a tool holder which is used with attaching the basal side of a shaft of the tool holder to a rotary part of a working machine, which has a holding portion for holding a tool such as a cutting tool, in the tip end side of the shaft, and which can correct runout of a tip end portion of the tool such as a cutting tool attached to the holding portion.
When a hole is to be opened in a workpiece or the inner face of a hole is to be ground by using a working machine or the like, a tool such as a cutting tool is attached to the tip end side of a tool holder mounted on a rotary part of the working machine. The tool in the tip end side of the tool holder is rotated at a high speed by rotating the rotary part of the working machine, whereby desired working can be performed on the workpiece for a short time period.
As described above, the tool holder is used in a high speed state. When the tip end of the tool attached to the tip end of the tool holder deflects even at a small degree as a result of the high speed rotation, there arises a problem in that the dimensional accuracy of the hole is lowered or the inner peripheral face of the hole is roughened to disable the hole from being accurately worked.
In order to solve the problem, conventionally, means for correcting vibrations of a shaft of a tool holder is disposed on the tool holder (see Japanese published unexamined Patent application No. 11-104931).
FIG. 12 shows the conventional art example. With reference to the figure, the conventional art example will be described. In a tool holder 1, the basal side 2 of a shaft 3 is formed as a shank portion 2 which is tapered as well known in the art, in order to fit the basal side into a tapered hole 1b of the main shaft 1a of a working machine which is not shown and has a well-known configuration. A holding portion 4 for a tool 4a is disposed in the tip end side of the shaft 3. (Usually, in order to fasteningly fix the tool 4a an example of which is a cutting tool such as a drill, a chuck 4 having a clamping hole which is expandable and contractable is disposed as the holding portion 4. In a well-known configuration, the cutting tool 4a may be attached directly integrally to the shaft 3 in the position of the chuck 4.) A large-diameter flange 5 which is used in the case where a grasping operation is to be performed by a grasping portion of a robot as well known in the art is formed on the outer periphery of the shaft 3 and on the side of the shank portion 2. The reference numeral 5adenotes a groove for engagement.
In the tool holder 1 shown in FIG. 12, plural radial holes 6 are threadedly formed in a bottom of the groove 5aof the flange 5, and a male screw 7 which is a screw member serving as a mass is screwed into each of the holes 6. A hexagonal hole 8 for a hexagonal wrench is formed in the head of each of the male screws 7. Each male screw 7 is adjusted so as to advance or retract in the corresponding hole 6 by using a wrench, so that, when the tool holder 1 is rotated at a high speed, the positional change in a radial direction appears as a change of the mass, whereby vibrations of the shaft 3 of the tool holder 1 can be corrected.
Even when vibrations of the shaft are corrected in a portion of the shaft 3 of the tool holder 1 the shaft center may sometimes deflect in a position closer to the tool attaching portion 4 in the tip end. Therefore, male screws 9 which similarly serve as a mass are attached to a tip end portion 3a so as to be advanceable and retractable, so that vibrations of the shaft in the tip end portion 3a can be corrected by advancing or retracting each of the male screws 9.
In the conventional art described above, however, the means for correcting vibrations of a shaft can correct vibrations of the shaft, only in a place where the correcting means is disposed and in the vicinity of the place.
In the case of a long tool such as a drill 4a which protrudes by a large distance from the tool attaching portion 4, the portion where correction of runout of the shaft center with respect to the rotation center is required at the highest degree is a blade edge 4b which is in the tip end of the drill. In the conventional art described above, however, it is impossible to correct runout of the shaft center with respect to the rotation center in a portion which largely protrudes from the tool attaching portion 4, such as the blade edge 4b in the tip end of the drill.
It is an object of the invention to provide a tool holder having runout correcting means for displacing an axis C of a tip end side of a shaft by a simple operation of rotating a screw member for pressurizing a part of the shaft, whereby a center of a tip end of a tool attached to a protruding tip end portion is made coincident with the rotation center Ca of the tool holder.
It is another object of the invention to provide a tool holder in which a screw member for displacing the axis C of the tip end side of a shaft is disposed in at least three or more uniform positions in the periphery of the main shaft of the tool holder, whereby, even when the shaft center of a cutting tool serving as a tool deflects in any direction, the tip end of the cutting tool can be moved to the rotation center of the tool holder irrespective of the direction.
It is a further object of the invention to provide a tool holder in which, even in a case where a screw member is disposed in one place, the position of the tip end of the cutting tool can be freely changed in either of leftward and rightward directions in accordance with the direction of rotation of the screw member.
It is a still further object of the invention to provide a runout correcting tool which is requested only to be attached to the periphery of a shaft of a tool holder that is already completed, whereby the tool holder can be changed to a tool holder having runout correcting means for displacing the axis C of the tip end side of the shaft to make the center of the tip end of a tool attached to a holding portion with largely protruding therefrom, coincident with the rotation center Ca of the tool holder.
Other objects and advantages will easily become apparent from the accompanying drawings and the following description relating to the drawings.
The invention has the following feature. A tool is attached to a holding portion at a tip end portion of a shaft. In the case where a drilling or cutting work is to be conducted, even when the position of the tip end of the tool is laterally shifted to deviate from the rotation center of a tool holder, a screw member is rotated to generate a force of displacing the axis of the tip end side of the shaft, between two contact portions of the tool holder, whereby the position of a blade edge of the tool can be easily moved toward the rotation center of the tool holder so as to coincide therewith. According to this configuration, it is possible to attain an effect that, in the case where a drilling or cutting work is to be conducted by rotating the tool holder at a high speed, precision working can be accurately performed.